U.S. patent application number 09/913032 was filed with the patent office on 2002-09-12 for reciprocating compressor and method for lubricating the reciprocating compressor.
Invention is credited to Fujii, Toshiro, Nakane, Yoshiyuki, Tarao, Susumu.
Application Number | 20020127117 09/913032 |
Document ID | / |
Family ID | 18402678 |
Filed Date | 2002-09-12 |
United States Patent
Application |
20020127117 |
Kind Code |
A1 |
Fujii, Toshiro ; et
al. |
September 12, 2002 |
Reciprocating compressor and method for lubricating the
reciprocating compressor
Abstract
In a reciprocating compressor, an adequate lubricating effect is
ensured for a sliding surface between a piston and a cylinder bore,
and the leakage of a refrigerant for discharge is prevented. After
a lubricating oil mixed within the refrigerant is separated by an
oil separator 23 on a discharge side, the separated lubricating oil
is guided via an oil supply hole 29 in a cylinder block 1 to the
sliding surface between the cylinder bore 12 and the piston 13 that
reciprocates within the cylinder bore 12 thereof in order to
lubricate the surface. In this reciprocating compressor, the
intermediate axial portion of the outer circumference of the piston
13 has a small diameter in order to define an oil sump 30. The oil
sump 30 is configured so as not to directly communicate with a
drive chamber 7, and oil always collects within the oil sump
30.
Inventors: |
Fujii, Toshiro; (Aichi-ken,
JP) ; Nakane, Yoshiyuki; (Aichi-ken, JP) ;
Tarao, Susumu; (Aichi-ken, JP) |
Correspondence
Address: |
Morgan & Finnegan
345 Park Avenue
New York
NY
10154
US
|
Family ID: |
18402678 |
Appl. No.: |
09/913032 |
Filed: |
August 8, 2001 |
PCT Filed: |
December 4, 2000 |
PCT NO: |
PCT/JP00/08589 |
Current U.S.
Class: |
417/269 ;
184/6.17; 184/6.8 |
Current CPC
Class: |
F04B 27/0878 20130101;
F04B 27/109 20130101 |
Class at
Publication: |
417/269 ;
184/6.8; 184/6.17 |
International
Class: |
F04B 027/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 12, 1999 |
JP |
11-349276 |
Claims
1. A reciprocating compressor comprising a cylinder bore and a
piston that reciprocates within the cylinder bore and guides a
lubricating oil to a sliding surface between the cylinder bore and
the piston in order to lubricate the sliding surface, wherein an
oil sump is defined on the sliding surface at which the lubricating
oil collects and does not communicate with a drive chamber to which
a base of the piston being faced.
2. The reciprocating compressor according to claim 1, wherein the
lubricating oil is separated from a refrigerant and is guided to
the oil sump due to a pressure differential between a suction side
and a discharge side.
3. The reciprocating compressor according to claim 2, wherein the
refrigerant is carbon dioxide.
4. The reciprocating compressor according to claim 1, wherein the
oil sump is defined around the entire circumference of the sliding
surface.
5. The reciprocating compressor according to claim 1, wherein the
oil sump is defined on the outer circumference of the piston.
6. The reciprocating compressor according to claim 5, wherein the
oil sump is defined on an intermediate axial portion of the outer
circumference of the piston that is formed to have a small
diameter.
7. A reciprocating compressor comprising a cylinder bore and a
piston that compresses a refrigerant drawn from a suction chamber
due to reciprocating movement of the piston within the cylinder
bore and discharges the refrigerant to a discharge chamber, wherein
the piston guides a lubricating oil, which is separated from the
refrigerant gas after discharge, to a sliding surface between the
cylinder bore and the piston due to a pressure differential between
a suction side and a discharge side, the reciprocating compressor
further comprising an oil sump defined on the sliding surface,
wherein the oil sump is defined at an intermediate axial zone on
the outer circumference of the piston having a diameter that is
smaller than both opposing sides of the intermediate axial zone,
wherein the oil sump always communicates with the discharge side,
which is the supply side of the lubricating oil, during the entire
stroke of the reciprocating piston, and the oil sump does not
communicate with a drive chamber that is the outflow side of the
lubricating oil, the drive chamber accommodating a cam plate for
driving the piston.
8. A method for lubricating a reciprocating compressor that
comprises a cylinder bore and a piston that reciprocates within the
cylinder bore that guides a lubricating oil to a sliding surface
between the cylinder bore and the piston in order to lubricate the
sliding surface, the method comprising guiding the lubricating oil
to an oil sump defined on the sliding surface and collecting the
lubricating oil in the oil sump and supplying the lubricating oil
from the oil sump to the sliding surface without causing the oil
sump to communicate with a drive chamber to which a base of the
piston being faced, while reciprocating the piston.
Description
TECHNICAL FIELD
[0001] The invention relates to a reciprocating compressor in which
a piston reciprocates within a cylinder bore and specifically
relates to a technique for lubricating the sliding surface between
the cylinder bore and the piston.
PRIOR ART
[0002] In reciprocating compressors, an oil separator is provided
on the downstream side of a discharge chamber, and after a
refrigerant gas is separated from a lubricating oil by the oil
separator, the lubricating oil is directed to and lubricates a
sliding surface between a piston and a cylinder bore due to the
pressure differential between the suction and discharge sides and
is then returned to a drive chamber on the low-pressure side.
[0003] In order to improve the effect of lubricating the sliding
surface between the piston and cylinder bore, the compressor has an
oil groove extending axially toward the outer circumference of the
piston. In a known configuration, the lubricating oil is supplied
from an oil hole and is guided to the sliding surface via the oil
groove, which actively communicates with the drive chamber. This
lubricating technique is disclosed, for example, in Japanese
Laid-open Patent Publication No. 10-141227.
[0004] However, in systems in which the lubricating oil is
separated from the refrigerant gas at the sliding surface between
the piston and the cylinder bore due to the pressure differential
between the suction and discharge sides, the use of a configuration
comprising the oil groove on the outer circumference of the piston
creates the problems of leakage of the refrigerant into the drive
chamber via the oil groove and a decrease in performance due to the
active communication of the oil groove with the drive chamber. This
phenomenon is particularly problematic in compressors that employ
carbon dioxide (CO.sub.2) as a refrigerant due to the large
pressure differential between the suction and discharge
pressures.
[0005] The invention has been designed with due consideration given
to these conventional problems and has objectives to facilitate an
adequate lubricating effect for the sliding surface between the
piston and the cylinder bore of a reciprocating compressor and to
prevent leakage of the refrigerant.
DISCLOSURE OF THE INVENTION
[0006] In order to attain the above objectives according to the
invention, an oil sump is provided on the sliding surface between
the piston and the cylinder bore in a reciprocating compressor. As
a result, the lubricating oil collects in the oil sump, the
lubricating oil ensures an adequate lubricating effect for the
sliding surface, and seizure is prevented. Moreover, a
configuration is taught in which the oil sump does not communicate
with the drive chamber, which is situated on the low-pressure side,
so that connection essentially occurs only via the gap between the
piston and the cylinder bore. This enables the amount of
refrigerant that leaks toward the drive chamber side to be reduced
and prevents a drop in performance.
[0007] Consequently, lubricating oil directed toward the oil sump
is preferably a lubricating oil separated from the refrigerant for
discharge, and a configuration in which the lubricating oil is
directed due to the pressure differential between the suction and
discharge sides is preferable. This construction is particularly
effective to reduce the amount of leaking refrigerant when utilized
with a compressor that uses carbon dioxide as the refrigerant.
[0008] It is also preferable to locate the oil sump around the
entire circumference of the sliding surface. In this case, the
entire circumference of the sliding surface is sealed and the
lubricating oil collects in the oil sump, which further reduces the
amount of refrigerant that leaks toward the drive chamber.
[0009] It is also preferable to dispose the oil sump on the outer
circumference of the piston. For this configuration, the
intermediate axial portion of the outer circumference of the piston
preferably has a small diameter. By disposing the oil sump on the
piston, the oil sump can be manufactured using the most commonly
known outer circumference processing methods in machine tooling and
as a result, the associated processing is easily performed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a cross section showing the reciprocating
compressor of the following embodiment.
[0011] FIG. 2 is an expanded view of Area A in FIG. 1.
[0012] FIG. 3 is a descriptive diagram showing a modified example
of the oil sump.
[0013] FIG. 4 is a descriptive diagram showing another modified
example of the oil sump.
[0014] FIG. 5 is a descriptive diagram showing yet another modified
example of the oil sump.
EMBODIMENT OF THE INVENTION
[0015] Hereinafter, an embodiment of the invention shall be
described with reference to the drawings. This embodiment, as is
shown in FIG. 1, is an application for a camplate-type
reciprocating compressor. A front housing 2 is joined to the front
end of a cylinder block 1, thereby forming part of the outer edge
of the compressor, and a rear housing 5 defining a suction chamber
3 and a discharge chamber 4 is joined to the rear end thereof via a
valve plate 6.
[0016] A drive shaft 8 is connected to a source of power and
penetrates through a drive chamber 7 formed in the front housing 2,
and the drive shaft 8 is rotatably supported by the cylinder block
1 and the front housing 2 via radial bearings 9 and 10. A
rotational cam plate 11 is contained within the drive chamber 7 and
the rotational cam plate 11 is anchored to the drive shaft 8.
[0017] The cylinder block 1 comprises a plurality of cylinder bores
12 penetratingly and circumferentially disposed and regularly
spaced, and pistons 13 are slidably disposed within the cylinder
bores 12. The base ends of the pistons 13 extend into the drive
chamber 7 and are coupled to the rotational cam plate 11 via a shoe
14.
[0018] Therefore, when the drive shaft 8 is rotated, the rotational
movement thereof is converted into linear reciprocating movement of
the pistons 13 by the rotational cam plate 11 and the shoe 14. Due
to the reciprocating movement of the pistons 13 within the cylinder
bores 12, a refrigerant in the suction chamber 3 is drawn into the
cylinder bores 12 via a suction valve (not shown) and then, while
being compressed, is discharged toward the discharge chamber 4 via
a discharge valve 15. The upper half of FIG. 1 shows one of the
pistons 13 at its top dead point and the lower half of the drawing
shows another one of the pistons 13 at its bottom dead point.
[0019] The radial bearing 10 is disposed within a circular hole
that is provided in the central portion of the cylinder block 1. A
thrust race 16 and a plate spring 17, which urges the rear portion
of the drive shaft 8 forward, are disposed on the bottom of the
hole. The urging force of the plate spring is supported by a thrust
bearing 18 disposed between the rotational cam plate 11 and the
front housing 2.
[0020] A chamber 19 is hollowed out in the central portion of the
cylinder block 1 and opposes the valve plate 6. The chamber 19 is
communicated with the discharge chamber 4 by a first discharge
pathway 20 near the mid-section in the vertical direction and
communicates with an external circuit, which is a refrigeration
circuit, via a second discharge pathway 21 on the upper side. A
fixture 22 for affixing the discharge valve 15 to the valve plate 6
is penetratingly located in the first discharge pathway 20.
[0021] A centrifugal-separation-type oil separator 23 for
separating the lubricating oil from a highly pressurized
refrigerant gas sent through the chamber 19 to the refrigeration
circuit is provided within the chamber 19. The oil separator 23
comprises a base 25 with a separation chamber 24 having a bottomed,
circular hole shape and a gas duct with a flange 26 attached to the
base 25 so as to hang concentrically from the edge of the upper
opening of the separation chamber 24. The separation chamber 24
communicates with the first discharge pathway 20 via a hole 27 that
penetrates a side wall of the base 25. The hole 27 opens almost
tangentially to the inside of the separation chamber 24.
[0022] Therefore, the lubricating oil is introduced into the
separation chamber 24 with the refrigerant so that it travels from
the first discharge pathway 20 through the hole 27 to rotate along
the periphery of the gas duct 26, the lubricating oil then collides
against the circumferential wall of the separation chamber 24 due
to centrifugal force, separates from the refrigerant and flows
downward, passes through a penetrating hole 28 located in the
bottom wall of the oil separation chamber 24, and collects at the
bottom of the chamber 19.
[0023] The refrigerant for discharge that is separated from the
lubricating oil, on the other hand, is sent to the refrigeration
circuit from the gas duct 26 via the second discharge pathway
21.
[0024] An oil supply hole 29 is provided in the cylinder block 1 in
order to guide the lubricating oil that has collected in the
chamber 19 to the sliding surface between the pistons 13 and the
cylinder bores 12. The oil supply hole 29, on one end, is
communicated with the bottom surface of the chamber 19, and on the
other end, with an oil sump 30 disposed on the sliding surface
between the pistons 13 and the cylinder bores 12.
[0025] In this embodiment, the oil sump 30 is formed by providing a
small-diameter portion on the intermediate axial portion of the
outer circumference of the pistons 13. In other words, by utilizing
on the piston 13 a portion having a diameter less than the outer
diameters of the head of the piston 13 opposing the cylinder bores
and the base of the piston 13 facing the drive chamber 7, a
ring-shaped oil sump 30 is defined.
[0026] The oil sump 30, as is shown in FIG. 1, always communicates
via the oil supply hole 29 with the chamber 19, which is on the
discharge side, but does not communicate with the drive chamber 7
on the low-pressure side during the entire stroke of the
reciprocating pistons 13. In other words, each oil sump 30
communicates with the oil supply hole 29 at the base and head ends
of the pistons 13 even when the pistons 13 are located at the top
or bottom dead points while not communicating with the drive
chamber 7 even when the pistons 13 are located at the bottom dead
point. Each oil sump 30, as shown in FIG. 2, is configured so as to
communicate with the drive chamber 7 via the smallest clearance C
(hereinafter referred to as a "side clearance") that is necessary
to ensure the proper sliding action of the pistons 13 against the
cylinder bores 12. The head of each piston 13 includes a piston
spring 13a.
[0027] In the compressor of this embodiment, which is configured in
the manner discussed above, when the pistons 13, which are coupled
to the rotational cam plate 11 that rotates in conjunction with the
drive shaft 8, reciprocate linearly within the cylinder bores 12
and compression begins, the compressed refrigerant gas pushes open
the discharge valve 15, is discharged into the discharge chamber 4,
and is then introduced into the chamber 19 from the first discharge
pathway 20. The lubricating oil in the refrigerant gas introduced
into the chamber 19 in conjunction with rotation is separated from
the refrigerant gas due to centrifugal force, flows down the wall
surface of the separation chamber 24 under its own weight, and from
the penetrating hole 28 collects at the bottom of the chamber
19.
[0028] In this manner, the lubricating oil separated from the
refrigerant gas that collects at the bottom of the chamber 19 is
sent through the oil supply hole 29 to and collects in the oil
sumps 30 on the outer circumferences of the pistons 13. The
lubricating oil is supplied to the sliding surface by the
reciprocating motion of the pistons 13 in order to lubricate the
sliding surface. Therefore, the sliding surface is reliably
lubricated and seizure is prevented.
[0029] The oil sumps 30 do not directly communicate with the drive
chamber 7, which is located on the low-pressure side, but rather
communicate via the side clearances C, so that a sealing effect due
to the lubricating oil collecting in the oil sumps 30 is attained,
and leakage of the refrigerant gas from the side clearances C is
prevented. As a result, the amount of refrigerant that leaks to the
drive chamber 7 is reduced. In this embodiment, the oil sumps 30
are located around the entire circumference of the sliding
surfaces, so that a drop in performance attributable to the leakage
of the refrigerant is prevented.
[0030] This design is even more effective when utilized with a
compressor that guides the oil under extremely high pressure, such
as a compressor that employs carbon dioxide (CO.sub.2) as the
refrigerant.
[0031] In this embodiment as well, a small diameter portion formed
in the intermediate axial portion of the outer circumferences of
the pistons 13 defines a ring-like oil sump 30, so that the oil
sump 30 can be processed using the most commonly utilized outer
circumference cutting methods in machine tooling, whereby the
associated production is easily performed. By providing the oil
sumps 30 in this embodiment, the area of the sliding surface
between the pistons 13 and the cylinder bores 12 can be reduced, so
that sliding resistance is reduced, and loss of power is
decreased.
[0032] The invention is not limited to the above embodiment and may
be appropriately modified within a range that does not diverge from
its fundamental nature. For example, although the oil sumps 30 were
defined by providing a small diameter portion on the outer
circumference of the pistons 13, the oil sumps 30 can also be
defined by forming a ring-like recess on the inner surface of the
cylinder bores 12 as shown in FIG. 3. In the alternative, the oil
sumps 30 can be defined on both the pistons 13 and the cylinder
bores 12.
[0033] The shape of the oil sumps 30 is not required to be limited
to a ring-like shape. As shown in FIG. 4, for example, the shape
can be modified to a substantially spline configuration with a
plurality of axially extending, linear grooves 30a that are
circumferentially disposed. In the alternative, a plurality of
ring-like grooves 30b can be axially formed in parallel to each
other on the outer circumference of each piston 13, as shown in
FIG. 5. The linear grooves 30a and the ring-like grooves 30b in the
configurations shown in FIGS. 4 and 5 must be mutually communicated
by a connecting pathway to neighboring grooves.
[0034] Furthermore, the oil sumps 30 are not required to be defined
around the entire circumference and may instead cover only a
portion of the circumference. It goes without saying that these
techniques can also be applied to a non-cam-plate-type compressor,
as long as it is a reciprocating compressor. Moreover, the oil
separator 23 is not limited to one that uses a centrifugal
separation method as the use of another separation technique would
not hinder the invention.
[0035] Industrial Applicability
[0036] As has been discussed above, the invention ensures reliable
lubrication for the sliding surface between the pistons and
cylinder bores, prevents burning, and prevents a drop in
performance attributable to leakage of the refrigerant for
discharge from the sliding surface.
* * * * *